The invention relates to a testing system for optical and electrical monitoring of the production quality and/or for determining optical and electrical properties of solar cells.
More particularly, it relates to a testing system of the above mentioned type which has a first conveyor device for conveying the solar cells to a test region, a second conveyor device for moving the solar cells through the test region, and a third conveyor device for conveying the solar cells out of the test region, and having an optical checking device, located in the test region, for visual checking of the solar cells, and an electrical checking device, also located in the test region, for checking the electrical functions of the solar cells, the electrical checking device including an illumination device for shining light on the light-sensitive surfaces of the solar cells and also includes an electrical contacting device for picking up voltages and/or currents at electrical contacts of the solar cells.
Such testing systems are typically equipped with the solar cells to be tested via a first conveyor device, in the form of a conveyor belt. In the test region, the solar cells are then taken from the first conveyor device by a robot and placed on an indexing turntable, where they are delivered, in timed increments to the optical checking device for visual checking and to the electrical checking device for function testing. In known testing systems, the optical checking device as a rule includes a area scanning camera, which in the stopped times in the cycle detects the surface of the solar cell to be tested.
Any irregularities are then recognized either by a human or by an assessment computer, and the applicable solar cell is classified as unacceptable or only limitedly acceptable in the cycling of the indexing turntable, and electrical contacting with the solar cell to be examined is then done at a different point in the test region, for checking the electrical functions. In the process, light is shone on the light-sensitive surface of the solar cell, and at corresponding contacts of the solar cell, the current and/or voltages that occur are measured. The electrical checking is typically also done during a stopped time of the indexing turntable.
After the conclusion of the checking operations, the checked solar cell is taken from the indexing turntable again by the same robot arm or a different one and transferred to a third conveyor device, where it is assigned to a defined quality class in accordance with the outcomes of the check and is carried away, usually with a linear belt device. The total cycle time for such a test cycle is between three and five seconds, in testing systems known at present.
However, besides this relatively slow cycle time, the known testing systems also have still other disadvantages:
Because of the use of robot arms and indexing turntables, such devices are relatively expensive and require a relatively large amount of space. When the solar cells to be tested are shifted from the first conveyor device to the second conveyor device and after the conclusion of the checking are shifted from the second conveyor device to the third conveyor device, damage often occurs in supplied or already-checked solar cells, so that on the one hand there are discards and on the other the ensuing sorting by quality classes is not completely reliable.
When the solar cells to be tested are fastened in the holder devices of the indexing turntable, the solar cells usually have a certain waviness, which in turn can impair the precision and conclusiveness of the optical checking.